The one thing (and I think most people don't like about the ER4S) is getting a balanced seal. For me, too much pressure can make the mids sound sucked out, too shallow and everything is tinny. Just right and I get the clarity, bass oomph, treble sparkle and soundstage height out of these.
I like using the grey tips as they're easier to insert, but they don't provide a satisfying enough sound. The white tips are much harder to insert, but they sound so much nicer when inserted right.
Yes. The key is to have a neutral air space. No vacuum. The easiest way to do that it to slightly moisten the tips and rotate them as you insert them. (that's what she said)
If you can create a seal with no pressure or vacuum that is at a good depth you should hear the er4s as intended for the most part...
always thought the best way to that was to yawn.